The invention relates to a method of facilitating measurement of a transmission level, the method being used in a radio system which comprises at least one base station and terminal equipment; in which data is transmitted in a frame that comprises time slots; and in which the base station sends a broadcast that the terminal equipment uses in comparing the strength of signals received from different base stations.
The invention also relates to a method of facilitating measurement of a transmission level, the method being used in a radio system which comprises more than one base station and at least one terminal equipment; in which the transmission is modulated with a carrier; in which data is transmitted in a frame that comprises time slots; and in which more than one base station sends its own broadcast modulated with the same carrier, the broadcast being used by the terminal equipment in comparing the strength of signals received from different base stations.
The invention also relates to a base station arranged to be used in a radio system which comprises at least one base station and terminal equipment; in which data is transmitted in frames that comprise time slots; and
in which the base station is arranged to send a broadcast that the terminal equipment is arranged to use in comparing the strength of signals received from different base stations.
The invention also relates to a base station that is arranged to be used in a radio system which comprises at least one base station and terminal equipment; in which the transmission is arranged to be modulated with a carrier; in which data is transmitted in frames that comprise time slots; and in which the base station is arranged to send a broadcast that the terminal equipment is arranged to use in comparing the strength of signals received from different base stations.
In a typical time division radio system, such as the GSM (Global System for Mobile Communication), data is transmitted in frames each one of which comprises a predefined number of time slots. In a typical radio system, a base station continuously broadcasts a beacon signal in some time slot, so that the terminal equipments know the base station or stations in whose coverage area they are. The beacon signal can be a separate pilot signal or a broadcast on a broadcast channel. In prior art systems, a terminal equipment listens to the broadcast of its home base station, sent in the first time slot of the frame. The broadcast comprises information that is important particularly in the active mode when a traffic channel is used. From the home base station the terminal equipment obtains e.g. information on the basis of which it also listens to and measures broadcasts of adjacent cells. When the strength of the broadcast both of the home cell of the terminal equipment and of the adjacent cells are known, it is for example possible to decide which one of the base stations is the best candidate for a new base station in handover.
Particularly in base stations with low capacity and with a single transceiver, the requirement of broadcasting a continuous beacon signal prevents the use of such capacity and quality-improving characteristics as frequency hopping, discontinuous transmission, and power control. On the other hand, a broadcast sent only in the first time slot does not allow monitoring of broadcasts sent by the base stations, particularly not when the terminal equipment is in the active mode.
The object of the present invention is to provide a method that allows continuous measurement of the transmission power of adjacent cells without a separate beacon signal.
The object is achieved by a method as described in the introduction, the method being characterized in that the base station broadcasts in different time slots of successive frames.
The method of the invention is also characterized in that each base station broadcasts in different time slots of successive frames.
The base station of the invention is characterized in that the base station is arranged to broadcast in different time slots of successive frames.
The base station of the invention is also characterized in that more than one base station is arranged to send its own broadcast, modulated with the same carrier, in different time slots of the frame, and each base station is arranged to broadcast in different time slots of successive frames.
Major advantages are achieved by the method of the invention. The invention allows continuous measurement of transmission power, as well as monitoring of broadcasts even when the terminal equipment is in the active mode. These facilities are utilized, for example, in handover.